package canvas import ( "syscall/js" "time" "git.kirsle.net/apps/doodle/lib/events" ) // Engine implements a rendering engine targeting an HTML canvas for // WebAssembly targets. type Engine struct { canvas Canvas startTime time.Time width int height int ticks uint32 // Private fields. events *events.State running bool textures map[string]*Texture // cached texture PNG images // Event channel. WASM subscribes to events asynchronously using the // JavaScript APIs, whereas SDL2 polls the event queue which orders them // all up for processing. This channel will order and queue the events. queue chan Event } // New creates the Canvas Engine. func New(canvasID string) (*Engine, error) { canvas := GetCanvas(canvasID) engine := &Engine{ canvas: canvas, startTime: time.Now(), events: events.New(), width: canvas.ClientW(), height: canvas.ClientH(), queue: make(chan Event, 1024), textures: map[string]*Texture{}, } return engine, nil } // WindowSize returns the size of the canvas window. func (e *Engine) WindowSize() (w, h int) { // Good time to recompute it first? var ( window = js.Global().Get("window") width = window.Get("innerWidth").Int() height = window.Get("innerHeight").Int() ) e.canvas.Value.Set("width", width) e.canvas.Value.Set("height", height) return e.canvas.ClientW(), e.canvas.ClientH() } // GetTicks returns the number of milliseconds since the engine started. func (e *Engine) GetTicks() uint32 { ms := time.Since(e.startTime) * time.Millisecond return uint32(ms) } // TO BE IMPLEMENTED... func (e *Engine) Setup() error { return nil } func (e *Engine) Present() error { return nil } // Delay for a moment. func (e *Engine) Delay(delay uint32) { time.Sleep(time.Duration(delay) * time.Millisecond) } // Teardown tasks. func (e *Engine) Teardown() {} func (e *Engine) Loop() error { return nil }